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PostPosted: Sun Dec 27, 2015 2:43 pm 
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I think you need to try new tubes, an SFL-2 should not lack dynamics or overly mellow. Tubes that are past their prime will sound slightly dark and murky while otherwise functioning fine.


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 Post subject: Sonic Frontiers SFL-2
PostPosted: Tue Dec 29, 2015 4:07 pm 
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Try using balanced in and out. Dynamics should be turbocharged!

But do get your tubes tested for gain by someone that knows what they're doing, not just transconductance. The trick is also understanding the preamp circuit to know which tubes are critical for gain and which ones are just output buffers. The critical ones should be gain matched internally (triode to triode) as well as tube to tube.

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PostPosted: Fri Sep 29, 2017 9:22 pm 
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Wasn't sure if I should start a new thread, but decided just to pick this one up again...

I bought a second hand SFL-2 a while back with complete crap tubes in it. In the meanwhile, I've never replaced the 6dj8's that came in the used SFS-80 i bought nearly 5 years ago. So I"m looking at buying new tubes for both--at total of 12 tubes, all 6dj8/6922.

The idea i'm toying with is buying 3 quads of different tube types. From reading this thread, for example, i'm being told that the back four positions on the sfl-2 are the critical ones, which leaves four up front, less critical. then there's the amp that could take another quad. then i figure i could swap a bit back and forth, between amp and pre, just to see what i hear.

Faced with buying 12 tubes, i really don't want to go much more than about $40/tube for the most expensive quad, and maybe $25-30 for the least critical. I'm thinking also of making at least one of these quads of the 7dj8 type, again, just for 'fun'...

Wondering if anyone has an opinion or two on (1) my idea to go with three separate quad sets, and (2) how i might want to split those up (tube types/brands).
Thanks for reading!

Other considerations...apart from the sfs-80, i also make extensive use of a halo-21 (which also has balanced inputs, btw, for those not already familiar with it. My main speakers are MG-12s, gunned.
edit: i listen to a wide variety of music, but i generally reserve the tubes for jazz and especially female vocals. i really enjoy what tubes can do with female vocals.

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PostPosted: Sat Sep 30, 2017 3:45 am 
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There is nothing inherently desirable about the 7DJ8, the only reason you see them being sold is because the proper 6DJ8 tubes are getting rare and expensive in certain old stock brands. The correct tube for that preamp is the 6DJ8 / 6922 / 7308 or russian 6H23.

Your can't slap in any old 6DJ8 / 6922 / 7308 / 6H23 tubes in your preamp and expect it to perform properly; preamps generally require tubes that have been tested and selected for low noise, and in many case it also requires matched tubes with balanced sections. Some brands of tubes are generally quiet, but that's still not as good as getting individually tested. Also not all positions will be sensitive to noise, the but ones which provide signal gain will.

The only place that actually tests tubes for noise that I know is Upscale Audio in California. Parts Connexion and The Tube Store test match tubes, but not noise. Having bought tubes from all three places over the years, I now only use Upscale Audio. I think you'll get excellent advise on which tubes to consider from Upscale, as they are familiar your preamp, and they sell more tubes than any other Dealer.


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PostPosted: Sun Oct 01, 2017 12:07 am 
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Actually, that's exactly who I've been looking at (Upscale). Any number of sites have suggested that in many cases the 7dj8 'can' be used in place of the 6dj8. but much like what you are suggesting, i wouldn't just want to jump in without hearing a bit more from other people. this is why (1) i posted here, and (2) i'm considering going with upscale--as they actually ask you what preamp you're using so they can provide feedback. obviously, as with any other seller, i have some reservations about just how much they are looking out for MY best interests, but at least it's good to hear from someone like yourself who can vouch for them.

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PostPosted: Wed Nov 15, 2017 4:32 pm 
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SSM DSB wrote:
-I once worked for SFI. Please... don't ask me to even try to explain all of the insanity that was going on there in the '90s. No... you REALLY don't wanna know what Jensen & Johnson were doing inside of that company; nor the events that transpired to cause its financial collapse. Why? Well... truth is often stranger than fiction. And hey... neither I nor my lawyers need the lawsuits for slander and/or libel.

-Anyhoo... for your SFL-2 or any of the line series pre-amps, try Siemens-Halske 7308 gold pins. Watch for fake tubes though. The real 1960's S-Hs are VERY expensive and only about 50% of them survive longer than a month in SFI units.

-The big problem with SFI's pre-amps is that they burn through exotic NOS tubes with an obscene frequency. The main reason for using what Johnson claimed were NOS Valvos in the Special Edition (S.E.) versions of SFI's pre-amps was that they're a hearty tube. The "Valvos" you've photographed have lightning fast transients, great highs, a semi-warm mid-range, and neutral mid-bass and low-bass. Not exactly the last word in warmth, but they're fast; lightning fast.

-I've also had some success with NOS Tesla E88CCs. They're an early 1970's tube, fairly robust, and deliver about 90% of what the S-H gold pin 7308s provide in the mid-range.

-As several other posters have suggested, look into upgrading the caps, the internal wiring, and even the o/p connectors on the back of the unit (i.e. try Nex-Gen RCAs). If you're thinking about using Johnson at PCx for these upgrades... well... think long & hard before dropping any coin. You'll might find that you get more mileage (sound & money wise) out of a parts upgrade that you install yourself (or have installed by a qualified bench tech).

Cheers... and best of luck with the upgrades.



Do you remember if SFI had a listening room for their products ?
Did they listen to their stuff before releasing for sales ?

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PostPosted: Wed Nov 15, 2017 5:10 pm 
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The Holland Amperex 6Dj8 being sold by Parts Connexion are a beautiful tube and at the sale prices an absolute bargain..I'm running them in my CDP right now and prefer them to some of the other "super tubes" I've tried...I ordered a back up pair...

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PostPosted: Thu Nov 16, 2017 3:12 am 
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terryakhan wrote:
SSM DSB wrote:
-I once worked for SFI. Please... don't ask me to even try to explain all of the insanity that was going on there in the '90s. No... you REALLY don't wanna know what Jensen & Johnson were doing inside of that company; nor the events that transpired to cause its financial collapse. Why? Well... truth is often stranger than fiction. And hey... neither I nor my lawyers need the lawsuits for slander and/or libel.

-Anyhoo... for your SFL-2 or any of the line series pre-amps, try Siemens-Halske 7308 gold pins. Watch for fake tubes though. The real 1960's S-Hs are VERY expensive and only about 50% of them survive longer than a month in SFI units.

-The big problem with SFI's pre-amps is that they burn through exotic NOS tubes with an obscene frequency. The main reason for using what Johnson claimed were NOS Valvos in the Special Edition (S.E.) versions of SFI's pre-amps was that they're a hearty tube. The "Valvos" you've photographed have lightning fast transients, great highs, a semi-warm mid-range, and neutral mid-bass and low-bass. Not exactly the last word in warmth, but they're fast; lightning fast.

-I've also had some success with NOS Tesla E88CCs. They're an early 1970's tube, fairly robust, and deliver about 90% of what the S-H gold pin 7308s provide in the mid-range.

-As several other posters have suggested, look into upgrading the caps, the internal wiring, and even the o/p connectors on the back of the unit (i.e. try Nex-Gen RCAs). If you're thinking about using Johnson at PCx for these upgrades... well... think long & hard before dropping any coin. You'll might find that you get more mileage (sound & money wise) out of a parts upgrade that you install yourself (or have installed by a qualified bench tech).

Cheers... and best of luck with the upgrades.



Do you remember if SFI had a listening room for their products ?
Did they listen to their stuff before releasing for sales ?


That's funny. I had a buddy who was working there as they were going tits up. He said they were slapping units just off the line into boxes and shipping them out. They didn't even test them. Huge numbers were coming back as defective.

So no, they did not listen to each unit.


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PostPosted: Fri Nov 17, 2017 7:25 pm 
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The Holland Amperex 6Dj8 are very nice sounding tube indeed, but you have to be careful when buying them NOS because some suffer from microphony issues. Anyway, as I said I used to own the SFL2 and subsequently the SF Line 3 preamps that I've enjoyed for many years. The best tubes that I used with them which serve me well and then some were the matched quad of EH 6922 tubes. They may not sound as lush as the Telefunken and or as sweet as the Amperex Bugle boys, but what they do is tread between the fine line of euphonic and neutral sound. Also, it lasted longer than most tubes that I used on the Sonic Frontier gears.


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